The present disclosure is generally related to a centralizer device and a method for deploying a bore hole component in a borehole. More specifically, the disclosure relates to a centralizer device that is caused to be released when the centralizer device is deployed in a desired position in a borehole, wherein the centralizer device has a trigger that secures a center positioning of the bore hole component inside the borehole.
When a well for production of hydrocarbons such as oil and gas is to be constructed, a bore hole is in the first place drilled and is afterwards typically equipped with a casing in the form of a steel pipe. Cement is pumped into the pipe from the inside top of the steel pipe. When the cement reaches the bottom of the borehole, the cement is squeezed between the bore hole and the outside of the pipe. One important measure of the quality of the well construction is the degree to which the steel pipe is centred in the bore hole after the cement has hardened. This measure is often called standoff. A standoff of 100% specifies that the steel lining is positioned exactly in the center of the bore hole and that the cement is distributed with a uniform thickness in the annular space between the bore hole and the exterior of the pipe. If the steel pipe is positioned so as to touch the bore hole, the standoff is 0% at this position. Previously, the American Petroleum Institute, Washington, D.C., (API) specified a minimum standoff of 67%. Some oil and gas exploration and productions companies, such as Statoil ASA, require a standoff minimum of 70%. (Ref.: Statoil ASA Technical Requirements: TR3519 “2.3.2 Centralization”.) In order to ensure controlled standoff, centralizer devices are used. Centralizer devices are devices such as, e.g., a simple bow-spring centralizer device that is described at the Uniform Resource Locator (URL) below:
http://www.glossary.oilfield.slb.cpm/em/Terms/c/centralizer.aspx.
Centralizer devices are positioned outside the pipe in a bore hole. Centralizer devices are positioned at an axial distance from each other that is so short, after hardening of the cement, that the pipe satisfies the requirements for standoff along the total length of the pipe. Bore holes that are curved or are horizontal will normally require that the axial distance between centralizers is shorter to compensate for increased load and tension in transverse direction to the longitudinal axis of the bore hole. The required axial distance between centralizer devices also depends on the respective diameters of the casing and bore hole. Centralizer devices are placed around a section of a casing when it is about to be lowered down in a bore hole. The centralizer device is often fastened directly to the casing and slides into the bore hole together with the section of the casing. Casings may keep standoff by centralizer springs in a centralizer device and more or less controlled strain between the outside of the casing and the wall of the bore hole. While the casing glides inwards, friction will naturally occur between said springs and the wall of the bore hole. A large friction may result in problems in deploying the casing. One may also experience that the centralizer device gets stuck or gets damaged so that the deployment is prevented or that the standoff becomes less than desired. This represents a trade-off between two contradicting requirements, on one side the centralizer device should be easy to deploy without incurring larger friction force than necessary, while on the other side should be standing as fixated as practically possible when the concrete flows downwards inside the casing and upwards on the outside of the casing and through all orifices of the centralizer devices. With unnecessary large friction forces, an increased risk of the centralizer device getting stuck and/or getting deformed or maybe destroyed may be experienced. This may result in the current requirements for standoff may get difficult to achieve.
When the casing is cast in cement, the cement inside the casing is normally drilled and what remains is a casing fixed by casting between the casing and the bore hole which is a good basis for further preparations for producing hydro carbon.
U.S. Patent Application Publication No. 2010/0078173 discloses a temperature controlled trigger device with which, e.g., a centralizer device may be deployed into a bore hole while it is fastened to a section of a casing. When the casing arrives at its longitudinal position, the centralizer device can be activated to spread out springs 12 that initially are placed along the casing and in this way do not spread out the springs 12 against the wall of the bore hole and create friction and other related problems. In said '173 publication, a so called memory alloy or SMA [“Shape Memory Alloy”] which is used for activation of a mechanism. SMA is a sort of metal alloy which is known to be deformable and to keep its deformed structure in a low temperature phase (in which the metal has a martensitic structure) and will thereafter resume its prior shape when it is brought into its high temperature phase/memory phase (in which the metal has an austenitic structure). The disclosed centralizer solves the problems with friction in the deployment phase in that the centralizer device in the first phase gets deformed to an appearance with a small outer diameter. When a casing having such a centralizer device is deployed down into a bore hole to where it is intended, the temperature thereafter has to be increased until it reaches the necessary temperature for the centralizer device mechanism to regain its high temperature phase resulting in the springs 12 of the centralizer device pressing against the wall of the bore hole. For this type of centralizer, the trigger temperature of the memory alloy must agree with the temperature relations in the particular bore hole. It is a problem that the trigger device is trigged at a temperature that is defined by the memory alloy and is difficult to adjust. The timing must also be sufficiently controllable in order to ensure that a practical method can be established to cause the trigger device to trigger when the casing is deployed at the correct place in the bore hole. The '173 publication also describes the possibility to lower the temperature in order for the memory alloy to keep its martensitic structure for a longer period in a deep bore hole. In this way such as centralizer may also be used for deep bore holes in which the temperature otherwise would cause triggering before the casing had reached the planned position. On the other hand, this would incur large costs.
U.S. Pat. No. 3,196,951 describes a centralizer with ribs formed as wires. These wires are separate parts that are to be installed on the centralizer before the entire assembly is slid onto a housing and the wires are fixed on the housing by stop collars 15, 16 and snap rings 17. When deploying the centralizer described in the '951 patent in a bore hole, the centralizer operates as an ordinary passive centralizer without means for reducing the mechanical resistance or improving the final centralization of the housing or other bore hole component.